This invention relates to a gas bubbler stone for metallurgical vessels having a porous, gas-permeable molded stone of a refractory material, a gastight partial sheathing surrounding it, made of a metal casing extending around the lateral peripheral surface of the molded stone and a sheet metal cover which covers the outer end face of the molded stone, and a gas delivery pipe which extends from the lower side of the sheet metal cover and is connected to the sheet metal cover in the area of a gas inlet opening formed in the area of a sheet metal cover and has a narrowed cross section at a distance from the gas inlet opening of the sheet metal cover, and a closing body which is movable at least in the axial direction of the gas delivery pipe is arranged in the pipe section between the sheet metal cover and the narrowed cross section, the cross section of this closing body being smaller than the inside diameter of the gas delivery pipe and larger than the narrowed cross section, and like a non-return valve, this closing body is loaded in the direction of the narrowed cross section which defines a valve seat by a helical compression spring that is supported on the sheet metal cover.
Such a gas bubbler stone is know from German Patent 33 41 446 C1. With this gas bubbler stone, breakthroughs of melt into the connected gas feed line can be largely prevented or their effects can be minimized. However, there is the problem with the known gas bubbler stone that the gas inlet opening becomes sealed by the helical compression spring at high gas pressures, which lead to complete compression of the helical compression spring.
Thus, there is the risk of the gas supply being interrupted precisely when a relatively high gas volume flow is needed.
The object of the present invention is to create a gas bubbler stone of the type defined in the preamble, which will minimize the risk of melt breakthroughs on the one hand while also on the other hand guaranteeing a reliable gas supply even at a high gas volume flow at a high gas pressure accordingly.
This object is achieved according to the present invention by the fact that the gas inlet opening is situated at least partially outside the partial circle of the compression spring.
The solution according to the present invention yields a bubbler stone, which minimizes the risk of melt breakthroughs as well as ensuring a supply of gas from the gas delivery pipe into the gas bubbler stone in the event that the helical compression spring is completely compressed because of a high gas pressure.
An advantageous embodiment of the gas bubbler stone according to this invention is characterized in that the gas inlet opening consists of three boreholes, whose center axes are each situated eccentrically with respect to the center axis of the gas delivery pipe. The center axes of the boreholes are preferably situated on a common circle and are spaced uniformly apart. In this way, a relatively large total orifice cross section and a stable abutment for the helical compression spring are achieved in the area of the gag inlet opening formed by the boreholes on the sheet metal cover.
Another advantageous embodiment of the gas bubbler stone according to this invention consists of the valve seat being designed in one piece with the gas delivery pipe. This reduces the number of individual parts to be joined, which reduces the manufacturing and storage costs for the gas bubbler stone.
According to another preferred embodiment, the sheet metal cover is designed like a plate and has a recess, which together with the bottom side of the molded stone defines a hollow space. The recess may preferably be produced with a suitable press. Again, this makes it possible to reduce the number of individual parts to be joined together.
Other preferred and advantageous embodiments of this invention are characterized in the subclaims.